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| IMAGE QUIZ ARCHIVE | ||||||
| Image Quiz | ||
| An Erosive Lesion of the Lateral Femoral Condyle of the Knee in an Eighteen-Year-Old Woman1 (continued) | ||
| Answer: A ganglion of the anterior cruciate ligament | ||
 Fig. 1-A |
 Fig. 1-B |
For larger view, click on image |
| Fig. 1-A Coronal magnetic resonance image shows the mass obscuring the anterior cruciate ligament and eroding the medial aspect of the lateral femoral condyle. Fig. 1-B The cyst, which had eroded a portion of the lateral femoral condyle, was approximately 1 cm in diameter. |
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| Magnetic resonance imaging revealed that the medial meniscus and posterior cruciate ligament were normal. The lateral meniscus had an incomplete discoid shape. A T1-weighted sagittal magnetic resonance image showed a large mass with low signal intensity that obscured visualization of the anterior cruciate ligament. The mass had high signal intensity on the T2-weighted sagittal magnetic resonance image. The coronal magnetic resonance image showed that the mass obscured the anterior cruciate ligament and had eroded into the medial aspect of the lateral femoral condyle (Fig. 1-A). The cyst that had eroded a portion of the lateral femoral condyle was approximately 1 cm in diameter (Fig. 1-B). | ||
| Arthroscopic examination confirmed that the lateral meniscus was an incomplete discoid shape. The anterior cruciate ligament appeared to be diffusely bulging and slightly blue in color (Fig. 2-A). The anterior wall of the cyst was excised with use of a motorized instrument, releasing a yellowish gelatinous material and exposing a slender anterior cruciate ligament (Fig. 2-B). The ganglion was adjacent to the anterior cruciate ligament and enclosed in a common sheath, and the cyst had eroded the medial aspect of the lateral femoral condyle. Repeat performance of the Lachman test and pivot-shift test showed a stable knee. | ||
 Fig. 2-A |
 Fig. 2-B |
For larger view, click on image |
| Fig. 2-A The anterior cruciate ligament appears to be diffusely bulging and slightly blue in color. Fig. 2-B The anterior wall of the cyst was excised with use of a motorized instrument, exposing a slender anterior cruciate ligament. |
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| Discussion | ||
| In our patient, the intra-articular ganglion cyst arose from the anterior cruciate ligament and eroded the medial aspect of the lateral femoral condyle. | ||
| The pathogenesis of ganglia remains unclear. Theories include mucinous degeneration of the connective tissue, herniation of the synovial tissue through a defect in the joint capsule, retention of ectopic presynovial tissue, and neoplastic degeneration of arthrogenous tissue. Congenitally displaced synovial tissue has also been considered to be a possible cause of ganglion formation. Since our patient had no history of knee injury, the cyst was probably a congenital abnormality. | ||
| Previous studies have described a reduction in symptoms after arthroscopic excision of ganglion cysts. Antonacci et al. reported that computed tomography-guided percutaneous aspiration was successful for the treatment of ganglion cysts associated with the anterior cruciate ligament in three patients. | ||
| Reference | ||
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